Process for the removal of unfixed developer powder from powdered electro-photographic reproduction coatings



PRQCESS Fon rrrr: nEMovAL or UNFrxEn DEVELOPER rownnn nnorvr rownnnnnELECTRO-PHOTOGRAPHIC RErnonrJcrroN COATINGS Martha Tornanek and WilhelmNengehaner, Wieshadeumesue assignments,

Biebrich, Germany, assignors, by

Ni, a corpoto Azoplate (Iorporation, Murray Hill,

ration of New Jersey No Drawing. Filed lune 16, 1960, Ser. No. 36,688

Claims. (Cl. 134-4 In the electrophotographic process for the productionof images, the latent image produced by the exposure to light of theelectrostatically charged photoconductive coating has to be developed, aprocess which generally takes the form of powdering over with apigmented developer, and then fixed, so that the powder imagebepermanently to the be carried out dicomes fused, and therefore adheressupport. The fixing of the image may rectly, i.el, the image may befixed to the surf-ace onducing coating of the unfixed pigmenteddeveloper powder adherent thereto. This is the case, forexample, ifdefective parts have to be removed from the image. In the case ofelectrophotognaphic material made of selenium, and equivalentsubstances, efforts are directed, in the interests of economy,,towardthe restoration of the photoconductive material to its original state,after the powder image has been transferred, so that the material can berecharged and used for the production of a freshimage.

The present invention is concerned with a process for the removal of theunfixed powder developer from powdered electrophotographic reproductioncoatings, in which process the pigmented developer is removed in simplemanner without the surface of the coating. undergoing damage. Theprocess accordant with the invention consists in the treatment of theunfixed powdered electro photographic coating with a mixture consistingof readily disperslbie parts of kieselguhr and etherified cellulose,with the possible addition of non-etherified cellulose.

All types of kieselguhr are suitable for the mixture accordant with theinvention. Purified kieselguhr is preferable, e.g. kieselguhr purifiedby treatment with hydrochloric acid and then calcined. Silicagel, whichis no natural silica substance, is also suitable. Examples ofetherification products of cellulose are cellulose alkyl ethers such asmethyl cellulose, ethyl cellulose, hydroxy ethyl cellulose,methylhydroxy ethyl cellulose, as also benzylcellulose and celluloseether carboxylic acids and their salts, e.g. cellulose glycolic acid andits sodium salt. The proportions of the components of the mixture usedas cleaning agent can vary within wide limits. From one to two parts ofkieselguhr to one part of cellulose component have proved advantageous.

The preferred average grain size of the kieselguhr is from about 5 toabout 20,4 and of the cellulose component from about 200 to about 600g.

I amaze Patented Aug. 13, 1963 The manner in which the process iscarried out is as follows: either the mixture accordant with theinvention is caused to disperse over the powdered unfixedelectrophotographic reproduction coating or over parts thereof fromwhich pigmented developer is required to be removed, or theelectnophotographic sheet is drawn through the mixture. No cracking orscratching of the surface of the coating occurs so that the nextelectrostatic images are not rendered defective.

The invention will be further illustrated by reference to the followingspecific examples:

Example 1 A mixture consisting of parts of kieselguhr and 50 parts ofmethylhydnoxyethyl cellulose is dispersed over an aluminum plate havinga vacuum-deposited selenium coating carrying an unfixed electrostaticpowder image. One passage over the electrostatic powder image issufficient to remove all visible traces of powder, while the seleniumcoating is unaffected.

Example 2 A mixture consisting of 100 parts of methyl cellulose and 100parts of lsieselguhr is dispersed over paper coated with zinc oxide andcarrying a non-fixed electrostatic powder image. The electrostaticpowder image is thereby quickly removed.

Example 3 After the production of an electrostatic powder image on analuminum foil coated with a photocondnctive organic substance-2,5 bis-(4- iethylamino-phenyhtl) 1,3,4-oxadiazole may, for example, be presentin the coat- A mixture composed of 50 parts of cellulose, 50 parts ofcarboxymethyl cellulose and 50 parts of kieselguhr is dispersed over apaper coated with zinc oxide and carrying a non-fixed powder image. Theelectrostatic powder image is removed and the coating remains unharmed.Instead of carboxymethyl cellulose, benzyl or hydroxyethyl cellulose maybe used.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the'invention includes all suchmodifications.

What is claimed is:

l. A process for the removal of unfixed powder developer inc-m powderedelectrophotographic reproduction coatings which comprises treating thecoating with a mixture of finely divided kieselguhr and finely dividedetheritied cellulose.

2. A process according to claim 1 in which the mixture also containsnon-etherified cellulose.

Carlson June 22, 1954

1. A PROCESS FOR THE REMOVAL OF UNFIXED POWDER DEVELOPER FROM POWDEREDELECTROPHOTOGRAPHIC REPRODUCTION COATINGS WHICH COMPRISES TREATING THECOATING WITH A MIXTURE OF FINELY DIVIDED KIESELGUHR AND FINELY DIVIDEDETHERIFIED CELLULOSE.